1. Field of the Invention
This invention relates to carbonless record materials. It more particularly relates to pressure-sensitive recording materials in the form of multi-ply carbonless record sheets and rolls. Such recording materials include colorless but colorable components, known as chromogenic materials, isolated to prevent coloration until the components are brought together.
Pressure sensitive recording materials, or carbonless papers, are mark forming systems and can be comprised of various arrangements of the mark-forming components and minute droplets of encapsulated solvent which, upon pressure release bring the mark-forming components into reactive contact. Many of these configurations are depicted in U.S. Pat. No. 3,672,935, which is hereby incorporated by reference. The most widely used configuration commercially is depicted in FIG. 2, view III, of said patent. In such a configuration the underside of the top sheet (the coated back or CB sheet) of a two-ply system is coated with a microcapsule layer wherein the microcapsules contain a solvent solution of chromogenic material, commonly called the colorformer. The top side of the bottom sheet (the coated front or CF sheet) is coated with a layer comprising developer material. To the uncoated side of the CF sheet can also be applied microcapsules containing a solution of color formers resulting in a pressure-sensitive sheet which is coated on both the front and back sides (hereinafter referred to as a CFB sheet). When said plies are superimposed, one on the other, in such a manner that the microcapsules of one ply are in proximity with the color developers of the second ply, the application of pressure, as by a writing instrument or impact printer, sufficient to rupture the microcapsules, releases the solution of color former and transfers color former solution to the CF sheet resulting in image formation through reaction of the color former solution with the color developer.
In a variation of the above-described arrangement, the solution of chromogenic material may be present as isolated droplets in a continuous pressure-rupturable matrix instead of being contained within discrete pressure-rupturable microcapsules.
In another type of pressure-sensitive carbonless system, known as a self-contained system, microcapsules and acidic color developer material are coated onto the same surface of a sheet, and writing or impact printing on a sheet placed above the thus-coated sheet causes the microcapsules to rupture and release the solution of chromogenic material, which then reacts with the color developer material on the sheet to produce a colored mark.
2. Description of Related Art
Vegetable oils have been identified as possible alternative solvents in pressure sensitive recording materials or carbonless papers. See for example U.S. Pat. Nos. 2,712,507; 2,730,457; 3,016,308; 4,001,140; 4,089,802. More recent examples of such vegetable oil based solvent systems for pressure sensitive recording materials include U.S. Pat. Nos. 5,177,051; 5,281,266; 5,464,803; 5,472,489; 5,476,829; and 5,605,874.
Despite these disclosures, it is only recently that some of these vegetable oil systems have been commercialized principally in some European countries, responding to market perceptions of a consumer preference for natural based systems.
Commercial acceptance of such recording systems in the United States has been slower due to drawbacks of many of these pressure sensitive recording materials relating to smudge, premature capsule breakage, odor and the ability to deliver images of sufficient intensity.
Additionally, vegetable and vegetable based oils are notably poor solvents. Although this can be an obvious advantage in certain environments, such as in contact with rubber or plastic printer components, nonetheless vegetable oil solvents are problematic requiring elevated temperatures such as 140.degree. C. to effect colorformer dissolution in the solvents. The vegetable oil solvents additionally can give rise to processing difficulties in achieving sufficiently small, less than 6 micron capsule sizes. It is an object of the present invention to disclose a novel carbonless paper especially suited for high temperature reprographic equipment environments such as xerographic machines, toner based copiers, laser printers and the like. This type of equipment often includes elements such as heated transfer rolls, fuser rolls, photoreptors, electronically charged drums or cylinders and other mechanical rollers, drums and other parts often operating at elevated temperatures. Since such machines can operate in enclosed facilities, minimizing odors is desirable.
The operating temperatures of such devices require specialized papers meeting stringent requirements for optimal performance.
A carbonless paper suitable for processing in elevated temperature reprographic equipment and achieving more intense imaging would be an advance in the art.